Machair Part 1: Biology and Ecology

MachairMachair is a very diverse coastal grassland, which is created through the complex interaction of physical factors with low-intensity agricultural systems [1, 2]. Machair grassland is found only on the north-western coast of Scotland and Ireland, with 50% of Scottish Machair found in the Outer Hebrides [2, 3]. As its global distribution is confined to around 25,000ha [4] machair is of national and international importance. The formation and continuation of machair is strongly associated with traditional agriculture by crofting communities and is therefore extremely susceptible to change in processes which create it [4]. Machair grassland is therefore very much a cultural landscape and its conservation depends upon the survival of crofting culture and the management techniques which create and maintain it [4]. These objectives provide key goals in an attempt to conserve the machair habitat.

  • Maintain traditional land-use
    • Particular emphasis on preserving low-intensity agriculture
    • Ensure that traditional crofting is financially viable
  • Secure robust plant and bird population
    • Protection of rare and threatened species
  • Plan for future
    • Coping with climate change
  • Educate locals and tourists
    • Importance and history of machair grassland
    • Complex interactions of machair habitat
    • Threatened and rare species
  • Ensure a successful long term management effort to mitigating threats to machair

Biology of Machair

Machair grassland is formed through a complex network of interactions, both biological and anthropogenic [4]. Peat or impermeable bedrock is covered over with windblown sand [5]; which is a product of glacial sediment and crushed shell. This is forced ashore through wave and wind action [3, 6]. The base-rich (pH 6.5-8.9) calcareous layer [3] which is formed promotes a plant and animal rich habitat [5] able to support up to 45 plant species in one square meter [6]. This high species diversity is facilitated by an extensive history of land management; in particular tillage and seasonal grazing [4]. This preserves a low sward and reduces the competitive exclusion of certain plant species [3]. The plant species which comprise machair vary with many biological factors such as; sand type, and structure, salinity, wind, the duration of winter flooding and sand burial responses [3, 7]. The 17,500ha of machair which is found in Scotland [4] has low productivity due to seasonal soil moisture fluctuations and low levels of soil nutrients such as phosphate, nitrate, manganese, copper, and potassium [3].

Typically machair occurs inland of a dune ridge, changing species composition marks this boundary e.g. sharp decline in Ammophila arenaria (European Marram Grass) abundance [3]. However the separation of these systems is debatable as the definition of machair is dubious, at times applying only to the grassy plain and at others relating to the whole system; from the beach to inland plains [6]. The EUNIS habitat type classification applies different codes to machair complexes; e.g. the whole machair system (X27) and machair grassland alone (B1.9) [8].Machair will be used here in reference to the short-turf grassland located above impervious bedrock; however this machair grassland cannot be separated from the complex machair system [4].

Ecology

The complexity and uniqueness of machair grassland makes it a key European and international habitat, to preserve it effectively its complex ecology must be understood and fully incorporated into any management strategy. Machair is an essential habitat for many rare plant and bird species [9]. An example of two such species is given below:

  • Spiranthes romanzoffiana (Irish lady’s tresses)
Irish Lady's Tresses

Figure 1: Irish Lady’s tresses (Spiranthes romanzoffiana) (Plantlife 2010)

Irish lady’s tresses (ILT) is one of the rarest orchids in Europe [6] its distribution is confined to just a few sites in Northern Ireland and the Scottish west coast and Western Isles, it also occurs in several sites in the Americas. ILT requires adequate light levels [10] and as machair systems are seasonally grazed, the removal of competing species creates a desirable habitat. Machair is also subject to seasonal inundation which is preferred by ILT [10].

ILT is vulnerable to many threats such as; the use of fertiliser, changes in land management, and drainage techniques [2, 9]. In the 1980s it was observed in around 70 sites, however as a result of these changes this has declined to only 11 sites [2] and at most of these sites it is in slow and continued decline [9]. Management techniques must therefore aim to conserve practices which create a desirable habitat for ILW.

  • Charadrius hiaticula (Ringed Plover)
Ringed plover

Figure 2 Ringed Plover (Charadrius hiaticula) (Life+)

The Western Isles provide an internationally important habitat for many wader species [11]. The machair systems found on the Uists support almost one third of the British Ringed Plover (RP) breeding population [6]. The Ringed Plover is thought to be one of the most dependent species upon machair [6] as it lays its eggs in the sandy soils [1]. Its numbers have declined by 67% since the 1980s across several study sites in the Uists [11]. Reasons for this decline have been associated with several factors such as egg predation by the hedgehog, introduced onto South Uist in 1974. Changes in agricultural practices have also been identified as a potential contributing factor in population declines [11]. It has been found that RP chicks which are hatched onto plough grow faster than those on grass; this may be due to the higher variety and abundance of invertebrates on cultivated machair [6]. The relationship with agriculture goes further still as the first egg laid coincides with the time of ploughing [12]. Of those which did nest on the machair grassland, few chose grass which was more than four years fallow [12]. This suggests a tight association of the RP with traditional machair agriculture, the conservation of this practice being essential to the conservation of machair and therefore the species which depend upon it.

References

Angus, S. 1998. ‘The conseration of machair in Scotland: working with people.’ People and Dunes, 177-91.

Calladine, J., Fuller, R. & Humphrey, L. 2011. ‘A survey of population changes in breeding waders on machair in Benbecula and North Uist: Annual surveys in 2008-2010 and changes since the mid-1980s.’ In S. N. H. C. Report (Ed.).

Cooper, A., McCann, T. & Ballard, E. 2005. ‘The effect of livestock grazing and recreation on Irish Machair grassland vegetation.’ Plant Ecology, 181, 255-67.

Davie, C. E., Moss, D. & Hill, M. O. 2004. ‘EUNIS Habitat Classification Revised 2004.’ European Environment Agency.

Edwards, K. J., Whittington, G. & Ritchie, W. 2005. ‘The possible role of humans in the early stages of machair evolution: palaeoenvironmental investigations in the Outer Hebrides.’ Scotland Journal of Archaeological Science, 32, 435-49.

EEA, E. E. A. 2007. ‘EUNIS Habitat Types- Machair.’

HIE, H. a. I. E. ‘Sustainable Tourism- challenges and opportunities.’.

JNCC 2010. ‘UK Biodiversity Action Plan Priority Habitat Descriptions.’

Life+ ‘Conserving Scottish Machair.’

Long, D. 2009. ‘Machair and coastal pasture: managing priority habitats for native plants and the significance of grazing practices ‘ Glasgow Naturalist, 25, 17-23.

Love, J. 2003. ‘Machair Scotland’s Living Landscapes.’ Scottish Natural Heritage.

NCMS, N. C. f. M. S. 2007. ‘Outer Hebrides Migratory Study Final Report.’ Western Isles Enterprise and Communities Scotland. Hall Aitken- experts in regeneration.

Owen, N. W., Kent, M. & Dale, P. 2000. ‘Ecological effects of cultivation on the machair sand dune systems of the Outer Hebrides.’ Scotland Journal of Coastal Conservation, 6, 155-70.

Owen, N. W., Kent, M. & Dale, P. 2004. ‘Plant species and community response to sand burial on the machair of the Outer Hebrides.’ Scotland Journal of Vegetation Science, 15, 669-78.

PDC 2004. ‘Plant Diversity Challenge- The UK’s response to the Global Strategy for Plant Conservation.’ Scottish Executive Environment and Rural Affairs Department.

Plantlife 2010. ‘Important Plant Areas (Scotland) ‘.

RSS, R. S. S. 2004. ‘Scottish Executive.’

TSG, T. S. G. 2011. ‘Farming and Rural Issues.’

Willis, A. J. 1989. ‘Coastal sand dunes as biological systems.’ Proceedings of the Royal Society of Edinburgh, 96:B, 17-36.

Wilson, J. R. 1978. ‘Agricultural influences on waders nesting on the South Uist machair.’ Bird Study, 25, 198-206.

Wilson, S. 2005. ‘Effects of land management on the location and status of populations of Spiranthes romanzoffiana in Scotland: a desk review and evaluation of the available evidence.’ Report to Plantlife.

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s